Thin Amorphous Carbon Layer Research Articles

Ion-implanted diamond films and their tribological properties

Abstract This paper reports the physical characterization and tribological evaluation of ion-implanted diamond films. Diamond films were produced by microwave plasma, chemical vapor deposition technique. Diamond films with various grain sizes (0.3 and 3 μm) and roughness (9.1 and 92.1 nm r.m.s. respectively) were implanted with C + ( m/e =12) at ion energy of 160 eV and a fluence of 6.72 × 10 17 ions cm -2 . Unidirectional sliding friction experiments were conducted in ultrahigh vacuum (6.6 × 10 -7 Pa), dry nitrogen and humid air (40% RH) environments. The effects of C + ion bombardment on fine and coarse-grained diamond films are as follows: the surface morphology of the diamond films did not change; the surface roughness increased (16.3 and 135.3 nm r.m.s.); the diamond structures were damaged and formed a thin layer of amorphous non-diamond carbon; the friction coefficients dramatically increased in the ultrahigh vacuum (0.1 and 0.4); the friction coefficients decreased slightly in the dry nitrogen and humid air environments.

Spatial resolution limits in EELS spectroscopy and imaging

In analytical problems, EELS is a powerful technique to locate, identify and measure the atoms contained within volumes of very small size. The present study is an experimental investigation of its resolution limits on a test specimen made of small metallic Tb and U clusters down to the atomic size and lying on a thin amorphous carbon layer. Several parameters have to be determined : the spatial resolution power (d), the minimum detectable concentration (Co) and the ultimate number of detectable atoms N = Co d2 tn within a specimen of local thickness t. The used instrument is a dedicated FEG-STEM VG HB 501 equipped with a Gatan spectrometer and governed by a home made digital acquisition system. This equipment offers unique capabilities for complete data quantification : the simultaneous acquisition for each pixel of two information channels (the annular dark field (adf) and the bright field one after the spectrometer) allows to discriminate the primary probe contribution from the inelastic effect. Sequences of up to 10 energy filtered images are acquired for different loss values covering the EELS range of interest from below the U-O45 edge (at 105 eV) to above the Tb-N4B edge (at 155 eV).

Epitaxial Copper Films Evaporated in Ultra-High Vacuum

Recent electron microscopy and diffraction studies of vacuum-deposited films have demonstrated the importance of temperature and surface condition of substrate in determining film structure and growth. Many interesting results of thin epitaxial films of face-centered cubic metals such as gold and silver have been reported. But, relatively few studies of copper have been made. The purpose of this study is to investigate structure and epitaxy of copper thin films evaporated onto various single-crystal substrates in an ultra-high vacuum.High purity copper was evaporated onto freshly cleaved (0001)MoS2, (100)NaC1, (001)mica and (11)CaF2 surfaces heated at temperatures between ∼25° and 200°C in a vacuum of ∼10-8 Torr. Average thickness of deposited films was about 90 Å. Deposition rate was about 0.4 Å/sec. The films were studied by reflection electron diffraction and transmission electron microscopy. Oxidation of copper films during preparation for electron microscopy and diffraction observation was minimized by deposition of thin layer of amorphous carbon upon freshly formed copper films.